Wga sta power saving

ABSTRACT

This invention relates to switching power saving modes and rescheduling communication frames for various periods of a beacon interval (BI) defined under WGA Draft Specification 0.8 for the personal basic service set (PBSS) and infrastructure BSS to achieve further power savings and other advantages. Stations can be awake during a contention-based period (CBP) if it is in active state and can schedule frames during a service period (SP) to allow the assigned receiver to transmit to the assigned initiator. Stations in a group can schedule a group address frame to be sent during the CBP and group SP of a specific periodic BI. Stations in peer-to-peer connection may directly notify its peer stations of its power saving mode and wakeup schedule. Stations of an infrastructure basic service set (BSS) can also use the same power saving mechanism as stations of a PBSS noting a difference where each BI will be an access point&#39;s (AP&#39;s) awake BI.

RELATED APPLICATION

This application claims the priority benefit of provisional applicationSer. No. 61/347,391 filed on May 22, 2010. The disclosure of theforegoing United States patent application is specifically incorporatedherein by this reference in its entirety and assigned toSTMicroelectronics, Inc., assignee of the present invention.

FIELD OF THE INVENTION

This invention relates to a method of saving power in wireless networkdevices, and more specifically, to a method of transmitting frames andswitching the power saving mode of WGA network devices.

BACKGROUND OF THE INVENTION

The Wireless Gigabit Alliance (WGA) Draft Specification 0.8 (WGA-D08),January 2010, herein incorporated by reference, defines modifications toboth the 802.11 physical layers (PHY) and the 802.11 Medium AccessControl Layer (MAC) to enable operation in the 60 GHz frequency bank(mmWave) for very high throughput wireless networks.

The personal basic service set (PBSS) is a self-contained network whichincludes one PBSS control point (PCP) and other stations (STAs).Wireless communication is possible to all member STAs of the PBSS. Theinfrastructure BSS is a network which includes one access point (AP) andset of stations (STAs) that have successfully synchronized with the APusing the JOIN service primitives and one STA that has used the STARTprimitive. Membership in a BSS does not imply that wirelesscommunication with all other members of the BSS is possible. An AP inBSS serves as gateway to access another network, e.g., the Internet.

Section 9.23 of WGA-D08 defines the mmWave channel access. Channelaccess by a mmWave station (mSTA) during the Beacon Intervals (BI) andis coordinated by a schedule. The schedule of the data transfer time(DTT) of a BI is communicated through the Extended Schedule element inthe Announce frame or the mmWave Beacon frame. The Extended Scheduleelement contains the scheduling information of all allocations in theDTT.

FIG. 1 shows an example BI structure as defined in WGA-D08. In a BI, theDTT is an access period during which frame exchanges are performedbetween STAs. The DTT is comprised of the contention-based accessperiods (CBPs) and service periods (SPs). SPs are allocated to specifictransmitting and receiving STAs, and CBPs are not specifically allocatedto any STA.

Section 11.2 of WGA-D08 defines power management modes for a wirelessdevice working under mmWave channels. Table 44 lists the various powerstates for PCP and non-PCP STAs during the various access periods of anAwake BI.

TABLE 44 Power management states for an Awake BI (selected portionsreproduced). PPS PS non- BI Portion PCP PCP STA CBP marked as PCPavailable in the schedule Awake Awake Doze CBP marked as PCP unavailablein the schedule Doze Awake Doze SP with broadcast AID as Destination AIDAwake Awake Non-truncatable or non-extensible SP with non-PCP AwakeAwake STA (excluding the PS STA) as Source AID and Doze Doze DestinationAID Truncatable SP or extensible SP with non-PCP STA Awake Awake(excluding the PS STA) as Source AID and Doze Destination AID SPsallocated to itself Awake Awake All other SPs Awake Awake Doze Doze

However, the power management states are generically defined. There aremany inefficiencies when working together with transmitting frames.Thus, there is a need for optimizing the switching of power managementmodes and transmitting frames.

Further, a mSTA may additionally work in an infrastructure BSS beyondthe PBSS. An infrastructure BSS contains an AP providing access toanother network, e.g., the Internet. All STAs within an infrastructureare required to be associated with the AP. WGA-D08 does not define apower saving mechanism for the infrastructure BSS; therefore, only802.11 baseline power saving mechanism will be used in 60 GHzinfrastructure BSS. Thus, there is a further need to implement a powersaving mechanism for mSTAs that can work with both PBSS and 802.11baseline power saving mechanisms.

SUMMARY OF THE INVENTION

The present invention is directed to a method of saving power inwireless network devices by switching power saving modes andtransmitting frames of a BI.

In one embodiment of the present invention, stations can switch to awakeduring a CBP. Stations can further eliminate an Announcement TrafficIndication Message (ATIM) frame from the BI.

In another embodiment of the present invention, stations in a group canschedule a group address frame to be sent during the CBP and groupaddress SP of an active group BI when all stations in the group are inactive mode.

In yet another embodiment of the present invention, stations can changethe transmission of frames during a SP to allow for the assigned serviceperiod receiver to transmit to the assigned service period initiator.

In further yet another embodiment of the present invention, stations inpeer-to-peer connection can directly notify their peer stations uponswitching back to active mode after switching to doze mode of its wakeupschedule and power saving mode.

In another embodiment of the present invention, stations of aninfrastructure BSS may use the same method of saving power as stationsof a PBSS noting a difference where each BI is AP's awake BI.

The foregoing and other features, utilities and advantages of theinvention will be apparent from the following more particulardescription of an embodiment of the invention as illustrated in theaccompanying drawings.

In addition, the features and advantages described in this disclosureand in the following detailed description are not all-inclusive. Manyadditional features and advantages will be apparent to one of ordinaryskill in the relevant art in view of the drawings, specification, andclaims hereof. Moreover, it should be noted that the language used inthe specification has been principally selected for readability andinstructional purposes and may not have been selected to delineate orcircumscribe the inventive subject matter; reference to the claims isnecessary to determine such inventive subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the BI structure as defined in WGA-D08;

FIG. 2 shows a Delivery Traffic Indication Message (DTIM) BI with agroup address frame in a CBP according to another embodiment of theinvention;

FIG. 3 shows a BI with a SP according to another embodiment of theinvention; and

FIGS. 4A and 4B show a PBSS under direct peer notification according toanother embodiment of the invention.

DETAILED DESCRIPTION

Embodiments of the present invention are hereafter described in detailwith reference to the accompanying figures. Although the invention hasbeen described and illustrated with a certain degree of particularity,it is understood that the present disclosure has been made only by wayof example and that numerous changes in the combination and arrangementof parts can be resorted to by those skilled in the art withoutdeparting from the spirit and scope of the invention.

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the present invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding, but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. Also, descriptions of well-known functions and constructionsare omitted for clarity and conciseness.

The invention relates to a novel method for saving power in wirelessnetwork devices. Embodiments of the invention are directed towardssaving power in WGA network devices by re-scheduling communicationframes and switching power saving modes for periods of inactivity. Themethod has added advantages of reducing retransmission, increasing theduration of the doze state for a device, and other advantages that maybe learned in practice by one of ordinary skill in the art.

An active STA or a power save STA in its awake BI is switched to theactive power management state during all CBP periods according to oneembodiment of the invention.

Referring to Table 44, a STA in active mode and a power save STA in itsawake BI can switch to doze mode in an awake BI during the CBP for anon-PCP STA. If a STA, e.g., STA1, transmits frames in a CBP to anotherSTA in active mode, e.g., STA2, the frame transmission cannot bereceived correctly by STA2 if STA2 is in doze state. STA1 may have toretransmit frames several times before the frames are received correctlyby STA2, thereby wasting power.

Section 11.2.3.1.3 of WGA-D08 further defines an Announcement TrafficIndication Message (ATIM) frame for an ATIM sender to notify that thereare buffered frames for ATIM destination. Before transmitting frames toa STA in active mode in the CBP, a directed ATIM frame to the active STAmay be required. This is not a good requirement, as explained in thefollowing example. In each BI, a STA, e.g., STA1, needs to send an ATIMframe to each STA, e.g., STA2, for which STA1 has buffered frames inactive mode so that STA2 will be awake in the CBPs. This makes the CBPtransmission complicated. However, if the protocol mandates that eachactive STA is to be awake in each CBP, then if a STA has frames for anactive STA, it can transmit frames to the active STA in each CBP withouttransmitting ATIM to the active STA.

Therefore, by mandating an active STA to be in awake state during allCBP periods, the complexity of power management is reduced byeliminating the need of transmitting the directed ATIM frame to theactive STA before transmitting frames to a STA in an active mode in theCBP. The result is increased bandwidth and power saving as well assimplifying the CBP frame transmission protocol.

FIG. 2 shows a DTIM BI with a group address frame in a CBP or SPaccording to another embodiment of the invention.

Group address frames are multiple destination broadcast frames that aSTA can send to a group of STAs in its group SP or a CBP in its activeBIs. However, with power saving mode considerations, other STAs may bein doze mode during such BIs. Thus, other STAs may not receive the groupaddress frame sent by the STA. In other words, if a STA wants to receivegroup address frames, it has to be active in each BI. This is not goodfor saving power, thus a need for improvement exists.

Specific periodic BI is defined according to one embodiment of theinvention. During such BIs, group address frames can be transmitted.During other BIs, group address frames are not transmitted. One exampleof a specific periodic BI can be a DTIM BI according to anotherembodiment of the invention. BI schedule 200 shows an example BIschedule consisting of normal beacon (NB) intervals 210, 220, 230, and aDTIM BI 240. Here, the group SP 241 is allocated in DTIM BI 240. Thegroup address frames are transmitted in the group SP 241. The groupaddress frames are transmitted in CBP 242 which is also allocated inDTIM BI 240. In normal beacon intervals 210, 220, 230, group addressframes are not transmitted.

FIG. 3 shows a BI with a SP according to yet another embodiment of theinvention.

Normally, a SP in a BI is assigned exclusively to the SP's initiator andthe SP's responder. Only the SP's initiator is allowed to transmit dataand/or management frames, and only the SP's responder is allowed toreceive such data and/or management frames if the reverse direction (RD)protocol is not supported. Therefore, bandwidth and power are wastedwhen the SP's initiator has nothing to transmit resulting in an idlechannel in the SP.

BI 300 shows an example BI consisting of SP 310 assigned to a SP'sinitiator STA1 and a SP's responder STA2 according to one embodiment ofthe invention. During a first period 320 of SP 310, STA1 may send dataand/or management frames exclusively, and STA2 may receive such framesfrom STA1 exclusively. When STA1 no longer has frames to transmit duringthe second period 330 of SP 310, it may be detected that the channelmedium is idle for a point (coordination function) interframe space(PIFS) in the SP. According to another embodiment of the invention, theMore Data bit in the frame control field of a data frame from SPinitiator STA1 can be set to ‘0’ to indicate that it has no more framesto transmit. Thereafter, the SP responder STA2 is allowed to transmitdata and/or management frames to SP initiator STA 1 during the thirdperiod 340 of SP 310. According to yet another embodiment of theinvention, STA1 and STA2 can also choose to go to doze state if the MoreData bit from SP initiator STA1 is set to ‘0’ to indicate that it has nomore frames to transmit.

FIGS. 4A and 4B show a PBSS under direct peer notification according tofurther yet another embodiment of the invention. PBSS 400 has PCP 410,STA1 420, and STA2 430.

Normally, the wakeup schedule (WS) and power saving mode of STA1 420 andSTA2 430 is stored with PCP 410. STA1 420 and STA2 430 can acquire thepeer STA's WS and power saving mode through PCP 410.

Referring to FIG. 4A, STA1 420 and STA2 430 starts peer-to-peercommunication 465. When STA2 430 changes from active mode to powersaving mode or have a new wakeup schedule, STA2 430 transmits a powersaving configuration to PCP 410 to be recorded. STA1 420, upon realizingthat STA2 430 is no longer in active mode by realizing that anunsuccessful transmission threshold has been reached, may transmit aninformation request 455 to PCP 410 asking for the WS and power savingmode of STA2 430.

However, a STA may not always know when to acquire such wakeup and powersaving schedule of its peer STAs if a STA changes from power saving modeto active mode. If STA2 430 returns to active mode, it is difficult forpeer STA1 420 to decide when to re-acquire the WS and power saving modeof STA2 430 from PCP 410.

Direct peer notification, especially when a STA only has one peer STA,makes this notification simple and reasonable. Referring to FIG. 4B,when STA2 430 changes its power save state and/or wakeup schedule, STA2430 may notify its wakeup schedule and/or power saving mode to peer STA1420 directly via action frame 466. One example of such action frame maybe information response frame. An information response frame is definedfor the direct peer notification to indicate a new WS. A successfulexchange of an information response frame between peer STA can be usedto indicate a power saving mode change according to an embodiment of theinvention.

An infrastructure BSS may also be adapted to use power saving modes andtransmission frames of a PBSS with some modification according toanother embodiment of the invention.

Section 11.2.3 of WGA-D08 discusses power management in a PBSS, butthere is no power save protocol defined for a WGA infrastructure BSS.Two possible methods for implementing a power save protocol for a WGAinfrastructure are using 802.11 baseline power save protocol defined for2.4 GHz/5 GHz infrastructure BSS or using PBSS power save protocol.However, neither of these two methods is entirely appropriate. The 2.4GHz/5 GHz infrastructure BSS does not have SP mechanism, and normallyEDCA is the medium access method in all BI. Therefore, the 802.11baseline power save protocol defined for 2.4 GHz/5 GHz infrastructureBSS is not appropriate for power save in a WGA infrastructure BSS. Withthe PBSS power save protocol, a PCP can be in doze state for severalBIs. Thus, this violates the rules of infrastructure BSS since an AP isalways awake in an infrastructure BSS in 2.4 GHZ/5 GHz band. Therefore,the unmodified PBSS power save protocol is also not appropriate for theWGA infrastructure BSS.

As such, the following describes power saving modes and transmissionframes adapted for an infrastructure BSS according to one embodiment ofthe invention.

An infrastructure BSS necessary consists of an AP and associated non-APSTAs. The AP, similar to the PCP in a PBSS, should operate under rulesdifferent from a non-AP STA. The AP can be in doze state in SPs that areneither the SP initiator nor the responder where the SP is not atruncatable or extensible SP, since such a SP is exclusively allocatedto SP's source and SP's destination. The AP will need to be awake inother periods of the BI. However, it is noted that the AP cannot sleepfor several BIs under the conditions. In other words, each BI will beAP's awake BI. Since the AP should otherwise always be active, CBP powersaving for the AP in an infrastructure BSS uses the same methods of CBPpower saving in PBSS CBP.

A non-AP STA may be in doze state in SPs that the STA is not the SP'sinitiator or responder in its active BI. A non-AP STA may also be indoze state in the CBP in its active BI if it is in power saving mode.However, the non-AP STA in active mode shall be awake during all CBPaccording to one embodiment of the invention.

It is further noted that an infrastructure BSS can further adapt thesame methods of SP power saving in a PBSS SP as discussed according toone embodiment of the invention.

A presently preferred embodiment of the present invention and many ofits improvements have been described with a degree of particularity. Itshould be understood that this description has been made by way ofexample, and that the invention is defined by the scope of the followingclaims.

1. A method of saving power for a station in a personal basic serviceset (PBSS) or infrastructure BSS, comprising: switching a mode of powersaving; and transmitting frames in a beacon interval.
 2. The method ofclaim 1, wherein the PBSS or infrastructure BSS comprises a mmWavenetwork.
 3. The method of claim 1, wherein the station is a non-PBSScontrol point (PCP) or non-access point (AP) active station.
 4. Themethod of claim 1, wherein switching the mode of power saving occursduring a period in a beacon interval.
 5. The method of claim 4, whereinswitching the mode of power saving comprises switching to being awake ina contention-based period (CBP).
 6. The method of claim 5, whereintransmitting frames comprises eliminating an Announcement TrafficIndication Message (ATIM) frame.
 7. The method of claim 1, wherein thebeacon interval is an active group beacon interval.
 8. The method ofclaim 7, wherein the active group beacon interval comprises a specificperiodic interval.
 9. The method of claim 8, wherein the specificperiodic interval is a Delivery Traffic Indication Message (DTIM)interval.
 10. The method of claim 7, wherein group address frames aresent during a contention-based period of the beacon interval.
 11. Themethod of claim 7, wherein group address frames are sent during a groupaddress service period of the beacon interval.
 12. The method of claim1, wherein a transmitted frame during a service period to allow for anassigned service period receiver to transmit to an assigned serviceperiod initiator.
 13. The method claim 12, wherein the frame from theinitiator comprising a data frame with a More Data bit set to ‘0’initiates transmission from the assigned receiver.
 14. The method ofclaim 12, wherein idling of a channel medium for a point interframespace (PIFS) period initiates transmission from the assigned receiver.15. The method of claim 12, wherein SP initiator and SP destinationswitch to doze mode after the transmitted frame comprising a data framewith More Data bit set to 0′ is transmitted by SP initiator.
 16. Amethod of saving power for stations in a personal basic service set(PBSS), comprising: establishing a peer-to-peer connection between afirst and second station; and sending an action frame comprising awakeup schedule and a power saving mode directly from the second stationto the first station if the second station changes a mode of powersaving from awake mode to doze mode after establishing the peer-to-peerconnection and then changes back to awake mode.
 17. The method of savingpower of claim 16, wherein the action frame is an information responseframe.
 18. The method of saving power of claim 14, further comprising:sending a power save configuration response frame comprising a wakeupschedule and a power saving mode from the second station to a PBSScontrol point (PCP); and receiving an information response framecomprising a wakeup schedule and a power saving mode to the firststation from the PCP.
 19. A method of saving power for a station in aninfrastructure basic service set (BSS), comprising: switching a mode ofpower saving comprising switching to doze mode in a service period wherethe station is not an initiator or a responder.
 20. The method of claim19, wherein the station is a non-access point station.
 21. The method ofclaim 19, wherein the station is an access point (AP) and whereinswitching the mode of power saving comprises switching to doze mode in aservice period where the AP is not an initiator or a responder and theservice period is not truncatable or extensible.
 22. The method of claim20, wherein the station is a power save station and switching the modeof power saving further comprises switching to doze mode in acontention-based period.
 23. The method of claim 20, wherein the stationis an active station and switching the mode of power saving furthercomprises being awake in a contention-based period.
 24. The method ofclaim 19, further comprising sending group address frames during acontention based period of an active group beacon interval.
 25. Themethod of claim 20, further comprising transmitting frames to anassigned service period initiator, wherein the station is an assignedservice period receiver.